With the All-Star Game over and regular-season games set to resume on Friday, the BP crew decided to rank the players who are likely to have second-half declines.

1. Jean Machi, Giants The hitting WPA (Win Probability Added) for the San Francisco reliever is .319, which is exceptional for a pitcher. Since 2000, only nine pitchers have posted a better hitting WPA, including the Cubs’ Travis Wood this season, Micah Owings three times and Mike Hampton duringhis seven-homer 2001 campaign. Hampton's .663 WPA that year remains the highest by any pitcher in the post-DH era. Machi is on pace to challenge it.But there's no reason to believe Machi is very good at hitting. Entering Friday, he’s 0 for 2 in his career. In his lone 2013 plate appearance, he struck out on three pitches against San Diego’s Huston Street. In one of Machi’s two plate appearances this season, he grounded out to second.

His WPA is based not on a true talent level but circumstances unlikely to be repeated. In his other plate appearance this season, Machi attempted a sacrifice bunt with runners on first and second and one out in the top of the 13th inning, a point to his credit. The opposing pitcher, Pittsburgh’s Jared Hughes, fielded the bunt and but threw it into right field, allowing a run to score and moving two Giants (including Machi) in scoring position. It's the 16th most important batting event by a Giant this year, by WPA. Ben Lindbergh wrote about players (like Kansas City’s Nori Aoki) who have demonstrated a true ability to reach base on errors, and it's possible that Machi is one of these guys. But predicting the future requires making some assumptions. I'm assuming Machi is not one of these guys.

Sorry, Jean. I hate to brush aside the good stuff you've done, but peripherals matter; process matters more than results. I doubt you'll keep this up. — Sam Miller

2. George Springer, Astros The problem with the Houston outfielder is not that he's lacking in power or speed, but rather that he's lacking in contact. His swing-hard-all-the-time approach has left him with the league's highest whiff rate, outpacing the likes of teammate Chris Carter, the Cubs’ Junior Lake, San Francisco’s Brandon Hicks and the Tyler Flowers of the White Sox. That's not an impressive group, with Carter (at .252) boasting the highest True Average of the four; Springer, for comparison, is at .295. Perhaps Springer will continue to look like an outlier, however, the degree to which he does so is likely to lessen. As great as power and speed are, batters need contact to make them play. Right now, that looks like a challenge for Springer. — R.J. Anderson

3. George Kottaras, Indians The backup catcher has a .714 slugging percentage. It’s tempting to just leave it at that. His career mark coming into the year? .406. He’s only had 27 plate appearances this season and he's been designated for assignment because Cleveland would rather have outfielder Chris Dickerson, who the Indians acquired in a trade on July 7, on the roster. So much for that.714 slugging percentage. — Jason Wojciechowski

4. The Martinezes, Tigers Who the heck turns into a power hitter at 35? Victor Martinez needs four more homers to equal his season best of 25, accomplished seven years in his prime. Or is this year his prime?

Some were concerned V-Mart wouldn’t return from his ACL injury two years ago. I figured he’d be able to climb back into a .300 singles machine. But his slugging is better than Miguel Cabrera this season. He’s also getting pitches to hit because the free-swinging J.D. Martinez, suddenly V-Mart’s protection, is mashing everything that moves. J.D. already has a career-best 12 homers, six of them in the ninth inning and four in blowout losses. He’s another nice story, because being released from Houston always contains the markings of a good comeback, but 1.000 OPSes are reserved for Hall of Famers, not fourth outfielders.

Once JD-Mart starts regressing, we’ll see V-Mart receiving fewer pitches to hit, along with his homer production. — Matt Sussman

5. Kurt Suzuki, Twins For this week’s Lineup Card, I decided to take a more scientific approach. I sorted all of the players by declining zone distance trend, such that the players were seeing pitches closer to the center of the strike zone as the season goes on. The logic of this idea was to isolate players who pitchers were challenging more aggressively in the center of the zone, possibly indicating that the player wasn’t as feared as they were formerly.

San Diego’s Jedd Gyorkocame up first by this method, but due to his injury, he won’t be playing again soon. Down the list, in the 12th spot, was Suzuki, who came from Oakland in the offseason to play a better than respectable catcher, even earning an All-Star nod for the hometown team. But in his last roughly 500 pitches in the majors, pitchers have decided to see how Suzuki responds to pitches in the dead center of the zone.

Suzuki’s zone distance is in a steady decline. He started the season strong, ringing up a 129 OPS+ in April/March, but his June fell back to a more pedestrian 102, and his last two weeks have been especially poor (.250/.302/.325). It may be the case that Suzuki has been figured out. PECOTA never bought Suzuki’s breakout, and discerningobservers couldn’t pinpoint any particular modification to Suzuki’s approach which would cause such a resurgence. It seems likely that Suzuki will regress. He’s a deserving All-Star on the basis of his first half play, but just don’t expect it to continue. — Rob Arthur

6. Danny Duffy, Royals Duffy’s 2.86 ERA in 18 games, including 12 starts, strikes me as unsustainable for the rest of the year. It would mark a substantial improvement in his performance that is not supported by his peripheral stats. Duffy throws 95 and has a suite of off-speed pitches, but his K rate is a pedestrian 19 percent — about his career average. He has improved his walk rate, but it’s still fairly high at nine percent (3.3/9 innings). His batted-ball tendencies have not changed, as he still has a strong flyball profile (35 percent GB). So, naturally, his .235 BABIP — 94 points below his only other somewhat-full season of 2011 — raises eyebrows. Duffy’s first-half FIP of 3.94 would probably give you a better idea of how he’ll play the rest of the year.

Also worth watching is whether he develops a heavy arm late in the year as he completes his recovery from Tommy John surgery. — Dan Rozenson

7. Mikie Mahtook, Rays (minors) People scan the Triple-A leaderboards in July and before you know it #free[player x] is twittering. It’s a surprise, for example, not to see #freeStevenSouzaJr (.361/.446/.602) all over the place. The news of the mostly prospect-free season (sound the well-is-drying-up alarm in Tampa Bay) in Durham has often focused on (#free?) Mikie Mahtook. The former LSU outfielder, now 24, has been aggressively promoted since the Rays drafted him with a supplemental first-round pick in 2011. He was assigned to Triple-A to start 2014 and has flourished. He’s hitting .311/.381/.502. His .191 ISO is a healthy leap in power, which hadn’t quite been there in his first two minor-league seasons. He has stolen some bases (12 of 14) and hit a few homers (seven), and he won’t embarrass himself in center field, where he mostly plays now that Kevin Kiermaier has gone up to the majors.

However: Mahtook’s numbers are skewed by a .402 BABIP, second in the league only to Washington’s Steven SouzaJr. Mahtook, who hits right-handed, is batting .467 against lefties after hitting a little over .250 against them in 2012 and 2013. Mahtook’s 0.36 BB/K rate isn’t pretty, and it’s not far out of line with his numbers from Double-A last season (if adjusting for a higher league). Nor was a scout at the ballpark recently much impressed by Mahtook’s outfielding. And Mahtook isn’t as fast as he looks, either.

The regression actually has already begun: On June 17, Mahtook was hitting .325/.399/.517. The Rays can certainly afford to wait. — Adam Sobsey

8. Teddy Roosevelt, Nationals racing president After collecting a total of 15 wins from 2008-13, Roosevelt has already claimed 14 wins this season. Sure, it can be argued that this is a just a continuation of the exponential improvement Teddy has been making since 2011. Sure, it can be said that he was called up too early, that giant president racing heads often take a long time to develop, that the addition of William Taft changes the entire dynamic, that Jefferson has lost a step and that Washington is probably racing injured. I'm still not buying it. The skills are still the same and there hasn’t been a change in Teddy’s approach. Buy the second half at your own risk. — Jeff Quinton